Porous diaphragm for electrolytic cells and method of producing same



Patented Mar. 28, I899. H. H. DOW. POROUS DIAPHRAGM FOR ELECTROLYTIC CELLS AND METHOD OF PRODUCING SAME.

(Application filed Sept. 19, 1898.)

(No Model) qwIh wooeo. WWW

m: u'onms ETERs co mom-mum. mswmarou. n. c.

FFTQEQ HERBERT H. DOW, OF MIDLAND, MICHIGAN.

POROUS DIAPHRAGM FOR ELECTROLYTIC CELLS AND METHOD OF PRODUCING SAME.

SPECIFICATION forming part of Letters Patent No. 621,908, dated March 28, 1899.

A Application filed September 19, 1898. Serial No. 691,369. (No model.)

To all whom it may concern:

Be it known that I, HERBERT H. DOW, a citizen of the United States, and a resident of Midland, county of Midland, and State of Michigan, have inventeda new and useful Improvement in Porous Diaphragms for Electrolytic Cells and Methods of Producing Same, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle so as to distinguish it from other inventions.

The annexed drawing and the following description set forth in detail one mode of carrying out the principle of my invention, such disclosed mode constituting one of various ways in which the principle of the invention may be used.

In said annexed drawing the figure represents a vertical cross-sectional View of the electrolytic cell used in my improved process, showing the electrodes in elevation therein.

Vhile the invention is applicable for use in electrolytic cells employing different electrolytes, it is principally intended for use in the electrolysis of natural brine or commonsalt solution into chlorin and sodium hydrate or of calcium-chlorid solution into chlorin and calcium hydrate.

The apparatus .consists of an electrolytic cell of suitable shape and dimensions having an anode B, made preferably of carbon, and a cathode C, also of carbon. The carbons are suitably insulated by means of rubber packing a, the gases being led off from the cell through the pipes a.

My method of obtaining the halogen chlorin consists in forming a diaphragm in the elec-- .and oxygen.

metallic iron F is introduced into the electrolyte in the neighborhood of the anode. On the electric current being passed through the solution the first actions that take place are the decomposition of the electrolytic solution near the anode and cathode, free chlorin being formed at or near the anode, and free sodium, calcium, and magnesium being formed at the cathode. These latter in turn react with the water of the electrolyte to form sodium, magnesium, and calcium hydrates, this formation also'taking place near the cathode, Na+H O:NaOI-I+H. Part of the chlorin at the anode combines With the iron and forms iron chlorid, (3Ol+Fe:FeOl The sodium,calcium, and magnesium hydrates and the iron chlorid diffuse toward the middle of the cell and meet between the electrodes. On such meeting the iron is precipitated as iron hydrate, Which forms part of the diaphragm,

3NaOH+FeGI Fe(OH) +3NaGl, 3Ca(OH) -]-2FeCl :2Fe(OH) |3OaCl Calcium and magnesium hydrates are precipitated by the sodium hydrate from the calcium and magnesium chlorid,

The diaphragm begins to form and build up from these precipitates, consisting of iron, calcium, and magnesium hydrates. The chlorin diffusing toward the cathode passing into the diaphragm is absorbed by the calcium and magnesium hydrates, forming calcium and magnesium hypochlorites, thus preventing the contamination of the cathode solution by the chlorin. These hypochlorites, whose formulae are not positively known, decompose very rapidly, probably into chlorid In actual working these hypochlorites are not found present. hydrate being inert so far as the chlorin is, concerned is not disturbed, so that eventually the side of the diaphragm near the anode is almost completely depleted of calcium and magnesium hydrates by the action of the chlorin, and only iron hydrate is left, While the cathode side consists mainly of calcium The iron ICO and magnesium hyd rates. The iron hydrate prevents to a great extent the ehlorin of the anode-compartmen t from being consumed by the parts of the diaphragm with which it will combine. The pores of the diaphragm containing iron, calcium, and magnesium chlorid, the sodium hydrate of the cathode side upon entering the diaphragm is absorbed by these chlorids before it can diffuse to the anode side, so that the sodium hydrate cannot contaminate the anode solution,

Thus the products of electrolysis are effectually prevented from passing into and con ta1ni nating the opposite solutions. The precipitation and formation of the diaphragm will take place most rapidly where the diffusion is the greatest, and should any portion become detached or mutilated diffusion will be greater at the mutilated point, and the consequent greater precipitation will mend the break. It is thus seen that the diaphragm will thicken evenly. While one or more sheets of porous materialsuch as paper, cloth, abestos, and the likemight be placed as a nucleus upon which the two essential layers of the diaphragm would be precipitated in the practical working of the cell, such a procedure has not been found necessary or advantageous, the diaphragm being readily produced in the proper place without such foundation. The physical qualities of the mixed hydrates when made into a diaphragm in this manner are such that they form a coherent and self-supporting mass imposing verylittle resistance to the passage of the electric current, butat the same time impose a high resistance to the diffusion of the products of electrolysis and the electrolyte.

In place of forming the iron chlorid in the cell by the action of the electrolytic chlorin on the metallic iron a solution of a soluble iron salt, such as ferrous sulfate, may be slowly added to the solution near the anode.

I have found that similar solutions of the alkali es or alkaline earths, including magnesium, may be treated in the above manner with like results.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, n'ovided the means covered by any one of the following claims be employed.

I therefore particularly point out and distinctly claim as my invention- 1. In a diaphragm, the combination of two layers, the one on the cathode side composed of a chemical substance which will consume free halogens by chemical action; the layer 011 the anode side composed of a different chemical substance that will not be consumed by free halogens and containing a substance with which any soluble alkali diffusing from the cathode side will readily combine chemieally, substantially as set forth.

2. In a diaphragm, the combination of two layers, the one on the anode side composed of an amorphous chemical substance that will not be consumed by free halogens and containing a substance with which any soluble alkali diffusing from the cathode side will readily combine chemically; the layer on the cathode side being capable of combining chemically with halogens, substantially asset forth.

3. In a diaphragm, the combination with a layer on the anode side consisting of a substance inert to halogens and containingasubstance capable of readily combining chemically with an alkaline substance, so that any alkali diffusing from the cathode-compartment, is completely destroyed; of a layer on the cathode side, consisting of a different chemical substance inert to alkaline substances and capable of readily combining chemically with halogens, substantiallyas set forth.

4:. In a diaphragm, the combination with a layer on the cathode side consisting of a substance entirely inert to an alkaline substance, of a layer on the anode side consisting of a different chemical substance and containing a substance capable of readily combining chemically with an alkaline substance, thus completely preventing the entrance of alkaline substances into the anode compartment,

substantially as set forth.

5. In a diaphragm, the combination with a layer on the anode side consisting of a substance inert to chlorin and containing a substance capable of readily combining chemically with sodium hydrate, the product of such combination forming the anode side of the diaphragm, of a layeron the cathode side consisting of a different chemical substance ontirely inert to sodium hydrate, and capable of readily combining chemically with halogens, substantially as set forth.

6. A diaphragm ,composed on the anode side of metallic hydrate or oxid other than that employed in the cathode layer and which is substantially inert to halogens and on the cathode side of alkaline-earth hydrates, substantially as set forth.

7. In a diaphragm, the combination with a cathode side consisting of a substance capable of chemically combining with halogens, of a layer on the anode side consisting of a hydrate or oXid of a metal substantiallyinert to halogens, substantially as set forth.

8. A diaphragm composed of iron hydrate or oxid on the anode side and otherhydrates on the cathode side, the latterhydrates capable of chemically combining with chlorin, substantially as set forth.

9. A diaphragm composed on the anode side of a metallic hydrate capable of being pre- IIC cipitated by calcium hydrate and composed on the cathode side of alkaline-earth hydrates, substantially as set forth.

10. A diaphragm composed of iron hydrate or oxid on the anode side and of alkaline, earth hydrates on the cathode side, substantially as set forth.

11. A diaphragm composed of iron hydrat on the anode side and calcium and magnesium hydrates on the cathode side, substantially as set forth.

12. The improved method of forming the porous diaphragm in electrolytic cells, which consists in slowly precipitating hydrates capable of readily combining with halogens, by the action of soluble alkali (as the latter is formed in the cell by electrolysis) on a soluble alkaline-earth salt, and the subsequent precipitation of another metallic hyd rate-substantially inert to halogens, by part of the alkaline-earth hydrate first precipitated, the method being carried out with solutions-of such composition that a coherent diaphragm is formed in place substantially as set forth.

13. The improved method of forming a porous diaphragm in electrolytic cells for the electrolytic production of chlorin, which consists in electrolyzing a solution containing a chlorid of an alkaline-earth base, whereby the hydrate of said base is precipitated adjacent.- to the cathode and introducing into the electrolyte in the neighborhood of the anode a soluble salt of a metal which will be precipitated as an insoluble metallic hydrate by the action of part of the the alkaline-earth hydrate on said salt, the method being carried outwith solutions of such composition by the iron of said salt is precipitated as an insoluble hydrate by the action of part of the alkaline-earth hydrate on said salt,the method being carried out with solutions of such composition that a coherent two layered diaphragm is formed in place wholly from the products of electrolysis, substantially as set forth.

15. The improved method of forming atwopart porous diaphragm in electrolytic cells for the electrolytic production of chlorin, which consists in electrolyzing a solution containing sodium, magnesium and calcium chlorids, and introducing into the neighborhood of the anode a soluble iron salt, whereby the hydrates of iron, calcium and magnesium are precipitated to form a coherent porous diaphragm, and whereby said calcium and magnesium hydrates are dissolved out of the anode side of said diaphragm by the action of electrolytic chlorin, the method being carried out with solutions of such composition that a coherent diaphragm is formed the anode side of the diaphragm consisting wholly of iron 11y drate, substantially as set forth.

16. An improved method of making two part diaphragms for the electrolytic production of chlorin, consisting in forming the diaphragm wholly by the action of electrolysis on the cell contents,consistin g in electrolyzin g a solution containing sodium, calcium and magnesium and iron chlorids, whereby the hydrates of calcium, magnesium and iron are precipitated near the cathode, and whereby said calcium and magnesium hydrates nearest the anode react on the iron salt there present,

precipitating iron hydrate, the method being carried out with solutions of such composition that a coherent diaphragm is formed wholly of hydrates in position where it is to'be used, substantially as set forth.

Signed by me this 17th day of September, 1898.

HERBERT H. DOWV.

Attest:

ALBERT POPKINS, DAVID '1. DAVIES. 

